const express = require('express');

const app = express();

​

app.use(express.json());

​

// Example route

app.get('/', (req, res) => {

  throw new Error('Something went wrong!');

});

​

// Error-handling middleware

app.use((err, req, res, next) => {

  console.error(err.stack);

  res.status(500).json({ error: err.message });

});

​

app.listen(3000, () => {

  console.log('Server is running on port 3000');

});

​

//app.js

//we need to put this code at last,this code run when there is no route match

app.all('*',(req,res,next)=> {

     const err= new Error(`Can't find ${req.originalUrl} on this server!`)

     err.status=404

     err.statusCode=404

    next(err)

})

//when we use next(err) it will go to error handling middleware and it will catch error and send response.

app.use((err,req,res,next)=> {

     err.statusCode= err.statusCode || 500

     err.status= err.status || 'error'

     res.status(err.statusCode).json({

          status:err.status,

          message:err.message

     })

})

​

function errorHandler (err, req, res, next) {

  if (res.headersSent) {

    return next(err)

  }

  res.status(500)

  res.render('error', { error: err })

}

​

npm install numeral

app.use((err, req, res, next) => {

  res.status(500).json({ message: err.message });

});